The meaning of the two words is identical, even though selber is somehow received as colloquial. This is also true when combined with Schuld. Note that Schuld is, depending on context, correct both upper- and lower-case:

selbst schuld sein

selbst Schuld haben

selber schuld sein

selber Schuld haben

(Examples by korrekturen.de)

I think they're both correct in any context, it's a matter of style (i.e. whether you're talking colloquial language).

Hey, just saw after writing this answer that I also wrote the accepted answer to the linked question. That explains why I was thinking that I already answered this question ;)
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OregonGhostDec 1 '11 at 17:22

Some context: A child would very probably say "selber schuld" to another child ("neener, neener"). An adult commenting on another adult having taken a big risk and failed would probably state "selbst schuld". The first one feels more teasing to me, and the latter more like a factual statement.
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fzwoDec 1 '11 at 17:27

I think that is really subjective, even though it emphasizes the fact that selber is regarded more as colloquial today, but the words do not actually imply that. If a child would say "selbst schuld", it would be the same. An internet/text message slang version is, by the way, sskm (selbst schuld, kein Mitleid), and you say that to others ;)
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OregonGhostDec 1 '11 at 17:29

Yes, it's subjective. That's why I've used "probably" and "feels" :) Though I do think "selbst" is too refined language for most children.
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fzwoDec 1 '11 at 18:42

@fzwo: Is "neener neener" a German or an English term? Is this what you meant? If so, do children use it in the same situation as "selber schuld"?
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user508Dec 1 '11 at 18:57